高居里温度Nd-Fe-B磁体的制备及温度稳定性研究

本文通过研究磁体(PrNd)27.8CoxDy3FebalB0.97(x=20,25)在不同热处理工艺下的磁性能、密度及晶粒大小,以探寻其最佳热处理工艺,并对磁体的温度稳定性进行了研究.结果表明:较高的Co含量使磁体的居里温度Tc大幅提高,但会导致内禀矫顽力Hcj下降;磁体的温度稳定性(温度系数与不可逆磁通损失hirr...     

低不可逆磁损磁体的研究

通过研究不同性能、不同长径比的圆柱体烧结钕铁硼样品在不同温度下的不可逆磁通损失,探究了烧结钕铁硼磁体不可逆磁损与内禀矫顽力、居里温度、长径比之间的关系,并阐述了磁体不可逆磁通损失的产生机制.本实验研制了一种具有中等矫顽力(Hcj = 1915 kA/m)、较高居里温度(Tc=449.7℃)的耐高温烧结Nd-Fe-B磁体...     

高性能烧结Nd-Fe-B磁体关键制造技术的开发与应用

烧结Nd-Fe-B永磁材料由于具有低成本、高磁性能而广受人们关注。近20年来，为了提高磁体的磁性能、温度稳定性能和抗腐蚀性能，国内外开展了大量的研究工作。据此，简要综述了近年来高性能烧结Nd-Fe-B磁体关键制造技术的开发与应用状况。     

Nd-Fe-B磁体烧结致密化过程的研究

定量描述了Nd-Fe-B磁体的烧结致密化过程, 分析了有效稀土含量、合金粉末粒度与烧结致密化过程的关系, 讨论了Nd-Fe-B磁体烧结过程的致密化机制. Nd-Fe-B磁体烧结致密化过程可分为3个阶段, 即致密化过程迅速进行阶段、缓慢进行阶段、相对稳定阶段;随着烧结温度的上升, 第一阶段表现得更为突出, 第二阶段对应的烧结时间区段大大缩短. 有效稀土含量的提高、合金粉末粒度的减小显著促进Nd-Fe-B磁体烧结致密化过程. 主相颗粒重排以及主相颗粒长大与形状适位性变化是Nd-Fe-B磁体烧结过程的两类主要致密化机制, 而且后者对于Nd-Fe-B烧结磁体实现完全致密化起着决定性的作用.     

添加Gd或Ho对烧结Nd-Fe-B磁体结构与性能的影响

添加不同数量的Gd或Ho,制备了(33-x)(Pr-Nd)-xGd-0.2Cu-0.75Al-1.10B -64.95Fe和(33-x)(Pr-Nd)-xHo-0.2Cu-0.75Al-1.10B-64.95Fe(x是质量分数,x=0,1,3,5)烧结磁体,分析了添加Gd或Ho对材料磁性能、温度稳定性及显微组织的影响....     

烧结Nd-Fe-B磁体晶界扩散TbH2高温稳定性及其机理

采用涂敷方式,在烧结钕铁硼表面均匀涂敷TbH₂粉末,经过不同的扩散温度处理,制备出晶界扩散磁体。研究了晶界扩散TbH₂对烧结Nd-Fe-B磁体常温磁性能及高温稳定性的影响,并分析了磁体矫顽力提升的机理。常温磁性能研究表明,扩散磁体经过890 ℃+490 ℃工艺处理后性能达到最优,矫顽力从1 383 kA/m提升到1 988 kA/m。高温磁性能结果显示,扩散磁体200 ℃的矫顽力温度系数|β|比原始磁体降低0.032%/℃,磁通不可损失hirr比原始磁体降低21.47%,扩散TbH₂明显提高了烧结Nd-Fe-B磁体的热稳定性。分析得出,晶界扩散TbH₂磁体矫顽力提升的机理是Nd₂Fe₁₄B晶粒外延层形成了（Tb, Nd）₂Fe₁₄B核壳结构,提高了磁晶各向异性场;同时改善了磁体的微观组织结构,有效地隔绝了晶粒之间的磁交换耦合作用。      

无重稀土烧结Nd-Fe-B磁体的显微结构和磁性能研究

对Ga、Al、Cu和Zr共同掺杂的烧结Nd-Fe-B磁体磁性能和显微结构进行研究,并通过回火工艺对磁体的矫顽力进行调控。结果表明：当一级回火为900℃×150 min,且二级回火为500℃×180 min时,磁体矫顽力H_cj从烧结态的14.33 kOe大幅提高到二级回火态的19.86 kOe,提高了38.6%;方形度H_k/H_cj由0.86增加到0.97;剩磁B_r仅从烧结态13.51 kGs略微下降到二级回火态的13.46 kGs;富稀土相分布更加连续和明显。研究分析表明,矫顽力大幅增加主要是由于含有少量的富Nd相和贫B相的烧结Nd-Fe-B磁体中Ga的掺杂改变了晶界相湿润性,降低了富稀土相中Fe元素的含量。本研究为无重稀土高矫顽力和高剩磁烧结Nd-Fe-B磁体步入产业化夯实了理论基础。     

烧结钕铁硼磁体的开发与应用

本文介绍了烧结钕铁硼 ( Nd- Fe- B)磁体的开发现状 ,并概述了国内外生产与市场应用。     

烧结Nd-Fe-B磁体废料回收Nd2O3的方法研究

采用硫酸复盐沉淀法、草酸二次沉淀法和磷酸盐沉淀法从烧结Nd-Fe-B废料中回收Nd2O3,先以硫酸或草酸对工业生产的Nd-Fe-B废料进行预处理,钕离子经碱化、酸溶解后,再分别采用草酸或碳酸铵沉淀而与铁分离,最后经煅烧得到Nd2O3粗产品.借助扫描电镜观察Nd2O3粉末形貌,并通过EDTA滴定确定Nd2O3产品的纯度并...     

高综合性能烧结钕铁硼磁体关键制备技术研究

通过优化合金成分设计和改进速凝片铸技术、烧结技术,在工业生产线上成功实现了40EH高综合性能烧结钕铁硼磁体的批量生产。SEM观察结果表明,磁体显微组织致密、精细而均匀;其平均晶粒尺寸约为5～6μm,不存在尺寸明显偏大的晶粒。在常温下,40EH烧结钕铁硼磁体的典型磁性能为Br=1.288 T,Hcb=996.8 kA.m-1,Hcj=2490 kA.m-1,Hk=2018 kA.m-1,(BH)max=322.0 kJ·m-3;其Hcj/79.6kA.m-1+(BH)max/7.96 kJ·m-3=71.7。在473 K高温下,40EH烧结钕铁硼磁体的典型磁性能为Br=1.056 T,Hcb=585.8 kA.m-1,Hcj=641.8 kA.m-1,Hk=520.2 kA.m-1,(BH)max=200.9 kJ·m-3;其J-H退磁曲线方形度较好,B-H退磁曲线仍然表现出比较明显的线性特点。在295～473 K温度区间,其剩磁与内禀矫顽力的温度系数分别为-0.101和-0.417(%.K-1)。当L/D=0.7时,在493 K保持2 h磁体开路磁通不可逆损失为3.8%左右。批量生产的40EH烧结钕铁硼磁体具有优异的常温磁性能,同时表现出良好的温度稳定性。     

Recycle for Sludge Scrap of Nd-Fe-B Sintered Magnet as Isotropic Bonded Magnet

The reduction diffusion method was performed for the sludge scrap of Nd-Fe-B sintered magnets with adding Ca metal to recover the oxidized Nd-Fe-B phase. After washing the resultant powders to remove Ca metal component, the powders obtained were recycled as an isotropic magnetic powder by the melt spinning method. The magnetic properties of powders as recycled were inferior, especially for the coercivity value, due to the deletion of rare earth metals during the washing process. The adjustment of metal composition, i.e., the addition of Nd metal, at the melt spinning process improved the magnetic properties to be Br=～0.75 T, Hcj=～0.93 mA·m-1, and(BH)max=～91 kJ·m-3. The magnetic properties of the bonded magnets prepared from the composition-adjusted powders were Br=～0.66 T, Hcj=～0.92 mA·m-1, and(BH)max=～70 kJ·m-3, which are approximately comparable to the commercially available MQPB boned one(Br=～0.73 T, Hcj=～0.79 mA·m-1, and(BH)max=～86 kJ·m-3).     

烧结钕铁硼永磁材料制备工艺的研究进展

对当前烧结钕铁硼永磁体制备工艺中速凝铸带、氢碎、烧结和热处理以及添加合金元素等工序进行了介绍,并对其研究进展进行综述。同时,对烧结钕铁硼永磁体行业可能的发展方向进行了展望。     

Grain Growth Behavior in Sintered Nd-Fe-B Magnets

The Nd2Fe14B grain growth behavior in sintered Nd-Fe-B magnets was quantitatively described.The effects of sintering temperature and time,and alloy powder size and its distribution on grain growth process were analyzed.Hence,possible grain growth mechanisms in these magnets were qualitatively discussed.The Nd2Fe14B grain growth proceeded at quite a high rate in the initial 0~1 h of sintering and from then onwards the grain growth rate decreased.A large average particle size or a wide particle size distribution of initial alloy powders was found to remarkably accelerate the grain growth process and even result in the occurrence of abnormal grain growth.On the basis of experimental results,two grain growth mechanisms were considered to operate during sintering of Nd-Fe-B magnets,that is,dissolution and re-precipitation of Nd2Fe14B particles,and Nd2Fe14B particle growth by coalescence.It was believed that Nd2Fe14B particle growth by coalescence not only produced a large average grain size and a wide grain size distribution,but also was the fundamental reason for the formation of abnormally large grains in the microstructure of sintered Nd-Fe-B magnets.     

Electrochemical Corrosion Behavior of Nd-Fe-B Sintered Magnets in Different Acid Solutions

Electrochemical corrosion behavior of Nd-Fe-B sintered magnets in nitric acid, hydrochloric acid, sulfuric acid, phosphate acid and in oxalic acid was studied. Potentiodynamic polarization curves and immersion time dependence of corrosion rates of Nd-Fe-B sintered magnets in different acid solutions were tested. Microstructures of corroded Nd-Fe-B sintered magnets were investigated by means of SEM and AFM. The results indicate that in strong acid solutions of similar hydrogen ion concentration, the corrosion current increases in the order of HCl 〉 H3SO4 〉 HNO3 solution and Nd-Fe-B sintered magnets are passivated in phosphate acid and oxalic acid. Within 25 min, the corrosion rates of Nd-Fe-B sintered magnets in H2SO4 and H3PO4 solutions show a declining trend with immersion time, while in HNO3 and HCl solutions the corrosion rates are rising. And in H2C2O4 solution, weight of the magnets increases. The brim of Nd-Fe-B sintered magnets is corroded rather seriously and the size of the magnets changed greatly in nitric acid. The surfaces of the corroded magnets in the above mentioned acid solutions are all coarse.     

Investigation of Abnormal Grain Growth in Sintered Nd-Fe-B Permanent Magnet

The abnormal growth of grains of sintering Nd13.6 Dy0.4 Fe79.5 B6.5 magnets were investigated in low oxygen manufacturing process.The abnormal growth of grains occurs easily when the sintering temperature is higher than 1080℃ during the manufacture process.In the magnets, the oxygen content is less than 700 × 10-6 and the average particle size of powder is smaller than 4 μm.The squareness of demagnetization curve of magnet is deteriorated.For high performance magnets, the abnormal growth grain should be avoided by selecting a suitable sintering temperature.     

钆对烧结钕铁硼磁体磁性能和相结构的影响

通过电弧炉冶炼合金,采用球磨制粉,在磁场下取向成型,真空烧结和热处理制备了Nd17-xRxFe76.5B6.5磁体,研究了在钕铁硼永磁体中用稀土Gd部分地代替钕时对永磁体的磁性能随Gd含量的变化。实验结果表明:在一定的烧结及热处理工艺条件下,Nd17-xRxFe76.5B6.5磁体在Gd含量小于5%(原子分数)时,Gd对磁体的剩磁和内禀矫顽力影响相对较小,当Gd含量5%时,磁体磁性能急剧下降。显微成分分析表明,在合金铸态下,Gd可抑制合金的α-Fe相的析出;在磁体中,Gd进入主相是降低磁体矫顽力的主要原因。     

钕铁硼永磁体电镀Ni-P非晶态合金镀层

研究了钕铁硼永磁体电镀Ni-P非晶态合金镀液组成、工艺参数和工艺流程,分析了影响镀层性能的影响因素,包括电流密度、温度、镀液的pH值及亚磷酸的含量等。测定了镀层与基体的结合强度;用中性盐雾试验评定了镀层的耐蚀性。结果表明,Ni-P非晶态合金化学稳定性好,耐蚀性优异,是钕铁硼永磁体的一种理想保护镀层。     

Nd-Fe-B永磁体化学镀Ni-Cu-P工艺研究

本文研究了烧结型 Nd- Fe- B永磁体化学镀 Ni- Cu- P的工艺过程 ,Nd- Fe- B永磁体经除油、封孔、出光后直接化学镀 Ni- Cu- P合金 ,可以获得与基体结合良好、耐蚀性高的镀层。